A few days ago we sent out an e-mail inviting users to update their data.
The list had been extracted from our CRM with about 16000 users.
The crm in question (old and unmanageable) did not keep the mails up to date and unknowingly we found ourselves with a large number of inactive mails.
The Amazon AWS SMTP service overnight sent a warning e-mail and shortly afterwards blocked the account because the bounce had exceeded 15%. The plugin did not detect the blocking or smtp errors and continued to send the mails even though nothing more was actually being sent; the number of mails certainly sent before the blocking was around 6000.
The final question is: how can one identify even approximately the mails that were not sent? In what order does the plugin send the mails? id order? alphabetical order?